BACKGROUND AND CASE: Simultaneous pancreas and kidney transplantation (SPK) is applied almost exclusively in C-peptide-negative type 1 diabetic patients, although some data on SPK in type 2 diabetes have been published as well. Nothing is known about SPK in the autosomal diabetes form, maturity-onset diabetes of the young (MODY). SPK was performed in a 47-year old man who has MODY3 because of a Arg272His mutation in the hepatocyte nuclear factor-1alphagene. He developed overt diabetes mellitus at 19 years and end-stage diabetic nephropathy 26 years thereafter. Before SPK, the patient had measurable fasting serum C-peptide levels, but lacked beta-cell response to intravenous glucose and glucagon. He was treated with 34 IU of insulin per day. At 2 years post-transplantation, the patient remains normoglycemic and insulin independent. A hyperglycemic clamp test showed a normal beta-cell function. CONCLUSION: Identification of MODY3 among all C-peptide-positive patients with advanced diabetic nephropathy might help to select a specific group profiting from SPK.